Recently, researchers at the Children’s Hospital in Boston analyzed aggregated data on users’ Facebook activity and interests to examine the connection between online social environments and obesity prevalence. They found that areas with higher percentages of people with interests related to healthy activities and fitness had lower obesity rates, while populations with a greater percentage of people who had liked or commented on television was an indicator of higher obesity rates.

Interestingly, the study found that social data about sports in general was not correlated with obesity because people may be merely watching sports or following it, not taking an active role in it.

The researchers, who published their findings in the journal PLOS ONE, not only determined that Facebook data could track obesity prevalence, they suggested that social networks could be used to explore additional conditions and deliver health interventions and public health campaigns.

“I’d hope that people would look to this data source to understand how it can improve our understanding of chronic diseases and population-level conditions,” Rumi Chunara, an instructor at Harvard Medical School and an author of the study, told me.

Chunara’s study isn’t the only one to test Facebook’s value as a tool for public health research. A study published earlier this year found that hospitals with more Facebook “likes” have lower mortality rates and higher patient satisfaction scores. And, citing a search for the word “Facebook” on PubMed (a public database of life sciences research), a recent Wired article reported that there have been about 400 academic papers published in the last four years that include the social networking giant.

Traditional public health research often consists of phone surveys that can require considerable amounts of money and time, but Chunara said a major advantage of using Facebook data is that you can reach a wide swath of people quickly and at a low cost. Facebook also enables researchers to drill down to specific neighborhoods and that kind of fine-grained data can be difficult to come by, she added.

Additionally, Facebook can provide real-time data, as well as the opportunity to explore how interactions with friends and contacts and health messaging could influence user behavior, the study said.

Still, despite Facebook’s advantages when it comes to public health research, it’s important to bear in mind the limitations of web and social data. As a February Nature article on the flaws in Google’s (s GOOG) flu-tracking techniques highlighted, social data doesn’t always mean what we think it does. For example, some researchers think that media hype about the flu this past season could have led to a volume of web searches for flu-related terms that was disproportionate to the actual threat.

But Chunara pointed out that there can be biases and issues with more traditional data sets as well. “Every data set has challenges and you have to definitely approach [them] carefully [so as] not be misled,” she said.